This invention relates to compositions and methods for the treatment/prevention of microbial diseases of fruit utilising specific yeast species strains. The invention also relates to biologically pure cultures of certain yeast strains and combinations thereof which are capable of treating/preventing microbial diseases of fruit.
Worldwide, post-harvest losses of fruits and vegetables have been estimated to be up to 50 percent of harvested crop and much of this is due to microbial diseases such as rots. In the USA, where more attention has been directed towards the post-harvest problem, losses of fruits and vegetables due to post-harvest spoilage still amount to about 24%. Pre-harvest losses of fruits and vegetables are also significant.
Fungicides, which are the principal means of controlling post-harvest rots and other microbial diseases, have recently come under security by health authorities in may countries in view of the potential effect of residues on consumers. According to a US National Science Academy Report (1987), as a class, fungicides account for 60% of the oncogenic risk among all the pesticides used for food produce. Furthermore, the US Environmental Protection Authority has recently proposed a ban on the use of ethylene bis-dithiocarbamates (EBDCs) on food crops. About one-third of all fruit and vegetables in the USA are treated with EBDCs. Benomyl, a fungicide widely used to protect apples and pears from attack by blue and grey mould, was also discontinued for post-harvest use in 1989.
Contamination of the environment by fungicides and risks to the health of farmers are other causes for concern.
A number of organisms are associated with microbial diseases of fruit.
At least 11 species of Penicillium have been isolated from pome fruits naturally infected with blue mould but P. expansum is by far the most common and economically important species. Blue mould, also known as soft rot and wet rot, is the most important post-harvest disease of apples and is also important on pears.
Grey mould is the most important post-harvest disease of pears and is second to blue mould in importance on apples. It is caused by the fungus Botrytis cinerea Pers. Also known as cluster rot or nest rot, grey mould can cause large losses because of its ability to spread from infected to adjacent healthy fruit during storage. The disease develops more rapidly at cold storage temperature than any other post-harvest decay except Mucor rot.
Mucor rot is caused primarily by Mucor piriformis E. Fischer. Mucor rot occurs less consistently than blue mould and grey mould, although in special situations it can cause several losses of apples and pears.
All of these rots are worldwide in occurrence, and affect many types of fruit.